Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $91.98   4.120%   $95.7696   $95.77   $95.75   $95.80  
  Purchase #2 $206.70   13.220%   $234.0257   $234.03   $234.05   $234.00  
  Purchase #3 $102.70   11.165%   $114.1665   $114.17   $114.15   $114.20  
  Purchase #4 $176.88   3.827%   $183.6492   $183.65   $183.65   $183.60  
  Purchase #5 $192.48   11.721%   $215.0406   $215.04   $215.05   $215.00  
  Purchase #6 $198.43   11.806%   $221.8566   $221.86   $221.85   $221.90  
  Purchase #7 $185.68   6.331%   $197.4354   $197.44   $197.45   $197.40  
  7 purchase totals = $1,154.85       $1,261.9436   $1,261.96   $1,261.95   $1,261.90